This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-146504 filed on May 16, 2001, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a compressor for compressing fluid, the compressor having a male-rotor and a female rotor engaging with each other. The present invention is applicable to compressors such as a screw-type compressor and a roots-type compressor.
2. Description of Related Art
In a compressor having a pair of rotors and a driving mechanism for driving the pair of rotors in synchronism with each other, a gear housing containing the driving mechanism therein is connected to a rotor housing containing the rotors therein. In case an inlet port for introducing fluid is formed in the rotor housing at a position close to the driving mechanism contained in the gear housing, lubricant in the gear housing tends to leak into the rotor housing due to a negative pressure developed in the rotor housing at a vicinity of the driving mechanism through a bearing supporting the driving mechanism. To avoid such a problem, the inlet port may be formed at a position far from the driving mechanism and the outlet port at a position close to the driving mechanism. In this manner, a positive pressure is developed in the rotor housing at a vicinity of the driving mechanism, and thereby leakage of the lubricant in the gear housing into the rotor housing can be avoided.
In this structure, however, the compressed fluid at a high temperature flows out from the outlet port formed at a vicinity of the driving mechanism. Therefore, the heat of the compressed fluid is transferred to the driving mechanism, and thereby the driving mechanism is heated to a high temperature. Accordingly, the driving mechanism has to be made to be durable to a high temperature. This results in a high manufacturing cost of the driving mechanism.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved compressor having the outlet port formed at a vicinity of the driving mechanism, in which the driving mechanism and other components are effectively cooled, and temperature of the compressed fluid delivered from the outlet port is lowered at the same time.
The compressor is composed of a pair of rotors rotating in engagement with each other and a driving mechanism for driving the pair of rotors. The pair of rotors is disposed in a rotor chamber formed in a rotor housing, and the driving mechanism constituted by plural gears is disposed in a gear chamber formed in a gear housing. The rotor chamber and the gear chamber are separated from each other by a separating wall of the rotor housing. Lubricant for lubricating the driving mechanism is encapsulated in the gear chamber. An inlet port for introducing fluid such as air into the rotor chamber is formed in the rotor housing at a position remote from the driving mechanism, while an outlet port for delivering compressed fluid at a high temperature is formed in the rotor housing at a position close to the driving mechanism.
The pair of rotors is rotated by a rotational torque transferred from a driving shaft via the driving mechanism. According to rotation of the pair of rotors, fluid is introduced into the rotor chamber from the inlet port and compressed therein, and the compressed fluid is delivered from the output port.
A first cooling water passage through which cooling water of an internal combustion engine circulates is formed in the gear housing at its bottom portion. The first passage is positioned at a vicinity of the outlet port. The lubricant in the gear chamber is effectively cooled by the cooling water flowing through the first cooling water passage, and thereby the driving mechanism and bearings supporting rotor shafts are cooled by the lubricant. The compressed fluid at a high temperature delivered from the outlet port is cooled by the cooling water at the same time.
A second cooling water passage communicating with the first cooling water passage may be additionally formed around the bearings fixed to the separating wall for supporting the rotor shafts. The bearings heated to a high temperature by the compressed fluid in the rotor chamber is effectively cooled by cooling water flowing through the second passage. Further, a third cooling water passage communicating with the first passage through the second passage may be formed at a bottom portion of the rotor housing, so that the compressed fluid in the rotor chamber is further cooled by the cooling water. Further, a communicating passage connecting a bearing hole containing the bearings therein and the gear chamber may be formed through the rotor housing to sufficiently supply lubricant in the gear chamber to the bearing hole.
According to the present invention, the driving mechanism in the gear chamber, the bearings supporting the rotor shafts and the compressed fluid in the rotor chamber are effectively cooled, and thereby durability of the compressor is improved. The cooling water passage or passages can be formed in the housings in an inexpensive manner.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.